Dynamic Custom Permission Registration for Django + DRF (thread-unsafe)

_dynamic_custom_permission_registration.md

dynamically registering custom permissions

if you use this method of declaring custom drf permissions for your custom django model's Meta class perimssions

it might get tiring and difficult to maintain if you manually define a new class for each custom permission.

you can dynamically register these custom model permissions as drf permission classes using a base class factory that dynamically sets the __init__() method.

apps.py

from django.apps import AppConfig

class YourappConfig(AppConfig):
    default_auto_field = 'django.db.models.BigAutoField'
    name = 'yourapp'
    def ready(self):
        from yourapp.services import cust_permission
        cust_permission.register_custom_permissions()

cust_permission.py

from django.contrib.auth.models import Permission
from typing import Iterable

class CustomPermission(BasePermission):
    def __init__(self):
        self.perms = ()
 
    def has_permission(self, request, view):
        if request.user.has_perms(self.perms):
            return True
        return False

    def has_object_permission(self, request, view, obj):
        return super().has_object_permission(request, view, obj)

def get_all(custom=True):
    try:    
        if custom:
            # custom permissions that don't follow default conventions
            # can also search using models' `Meta` classes
            perms = Permission.objects.all().filter(codename__regex=r'^(?!(add|change|delete|view)_).+')  
        else:
            perms = Permission.objects.all()
    except:
        perms = None
    finally:
        return perms

def get_all_permission_labels(custom=True):
    perms_q = get_all(custom)
    if perms_q:
        return [f"{perm.content_type.app_label}.{perm.codename}" for perm in perms_q]
    
def parse_permissions(permission_label:"str"):
    if type(permission_label) == str:
        return (permission_label,)
    else:
        raise Exception("invalid permission format. Each custom permission class can only have 1 custom permission")

def create_custom_drf_permission(name,permissoin_label:"str"):
    CustomClass = type(name,(CustomPermission,),{})
    def custom_init(self):
        self.perms = parse_permissions(permissoin_label)
    CustomClass.__init__ = custom_init

    return CustomClass

permission_store = {} 
def generate_custom_permissions():
    permission_labels = get_all_permission_labels(custom=True)
    for permission_label in permission_labels:
        class_name = permission_label.replace(".","App_") # replace illegal class name char, add some info
        permission_store[permission_label]=create_custom_drf_permission(class_name,permission_label)

def register_custom_permissions():
    generate_custom_permissions()
    import yourapp.permissions
    from django.conf import settings
    for PermTypeClass in permission_store.values():
        setattr(yourapp.permissions, PermTypeClass.__name__, PermTypeClass)
        settings.REST_FRAMEWORK['DEFAULT_PERMISSION_CLASSES'].append(f"yourapp.permissions.{PermTypeClass.__name__}") # requires this to be created in settings.py

def get_custom_permission_type_class(permissionLabel):
    return permission_store[permissionLabel] # might want to make this thread-safe in future

permissions.py

# empty placeholder module
# classes are registered by yourapp.services.cust_permission.register_custom_permissions

please let me know if you have a better solution! i have been searching for an easier way to no avail..